Bank of America is facing a $50 billion lawsuit that might prompt a big settlement.

According to Dealbook, a group of shareholders backed by some of the biggest class-action law firms is suing Bank of America for $50 billion, claiming the firm and its top execs committed securities fraud related to BofA's December 2008 acquisition of Merrill Lynch.

The lawsuit isn't new, it's been "working its way through the system" since soon after BofA's $50 billion acquisition of Merrill (recently, a judge allowed shareholders claims to proceed in August), however details about the case -- like that it seeks $50 billion -- and what it means for BofA are now more clear.

The shareholders claim that Bank of America "engaged in a deliberate effort to deceive the bank’s shareholders" about big losses looming at Merrill Lynch. The losses would hit BofA days after the acquisition.

The shareholders (Ohio Public Employees Retirement System, State Teachers Retirement System of Ohio, the Teacher Retirement System of Texas, Stichting Pensioenfonds Zorg en Welzijn, represented by PGGM Vermogensbeheer B.V., and Fjärde AP-Fonden) claim BofA execs, particularly former CEO Ken Lewis and former CFO Tom Price, knew the losses were over $10 billion and concealed details from other execs.

Dealbook says Lewis and Price might end up paying to settle the case. As for BofA, Dealbook says "the settlement value appears to be in the billions."

The trial is set for October 12 2012. Until then, a huge settlement, or even bigger lawsuit, looms over the firm's heads.

Dealbook's Stephen Davidoff writes, "a court will most likely calculate [the damages that might be owed plaintiffs] by referencing the amount that Bank of America stock dropped after the loss was announced; this is as much as $50 billion. It is a plaintiff’s lawyer’s dream. Bank of America is facing a huge liability from this claim."

One example of their claims against Bank of America and its execs, cited by Dealbook, is that the BofA CFO at the time, Joe Price, was aware in November that Merrill's books contained a $5 billion loss that BofA shareholders wouldn't find out about until after the Bank of America bought Merrill.

That loss ultimately amounted to over $15 billion. But in November, when the deal was in the final stages, there was a good reason for Price's decision not to disclose the known $5 billion loss to shareholders beforehand: Merrill was losing about that much per quarter anyway.

The deal was signed on December 5th. By then, the plaintiffs claim, Merrill's losses amounted to $11 billion. And, they allege, Price knew about it, and worse -- he told Mayopolous that the losses were billions less.

The acquisition issue has already sparked legal actions. The first, brought by the SEC, was settled for $150 million. The second will be brought by the New York AG, according to Dealbook. The amount it seeks is unknown.

This one is huge -- $50 billion. It could be disastrous for Bank of America's share price tomorrow. If it starts trading below $6, watch out. At that point, Bank of America might be worth more dead than alive.